1. Field of the Invention
The present invention relates generally to an optical image reader and more particularly to an optical image reader whereby a background color outside a document sheet can be changed.
2. Description of the Related Art
Optical image reading equipment is used as computer peripheral equipment to read by optical means two-dimensional image of a document. An image thus obtained is input to a computer for further processing. In recent years, various kinds of computer image processing have been developed. It is desired to obtain an image suitable for individual image processing.
In FIGS. 12 and 13, a conventional method is illustrated. As shown in FIG. 12, optical image reading equipment produces an image of a document 91 by detecting light reflected by document 91. A reading portion 90 having a light detection element (e.g. CCD) is provided to detect reflected light.
In reading portion 90, the reflected lights in an entire reading area, which is irrespective of the document size, are converted to electric signals to output an image data. The obtained image data, therefore, contains an image of document 91 as well as a background part 92 positioned outside document 91.
Now, when the image is processed in a recognition processing such as OCR (optical character recognition), a significant image such as image of characters in document 91 can easily be extracted if the color of background part 92 is the same as the texture color of document 91. For example, when reading document 91 having white texture as shown in FIG. 12, black color characters in document 91 can easily be recognized if background part 92 is white.
On the other hand, in case of image filing processing etc., images in entire part of document 91 must be extracted. Also as shown in FIG. 13, when document 91 is obliquely placed on a platen, the oblique movement must be corrected electronically. In such cases as extracting whole images of document 91, it is preferable that the color of background part 92 is different from the texture color inside document 91. As shown in FIGS. 12 and 13, image of document 91 having white texture can easily be extracted if background part 92 outside document 91 is black.
The above-mentioned color of background part is determined by a color of a backing member provided in the reading position. Such backing member is fixed in position in case of either a sheet-feed type image scanner, where an image is read while a sheet is transported in the sub-scanning direction, or image reading equipment having optical system provided in a fixed position for reading a sheet on a platen.
For the above reason, in order to obtain proper images, it is required to use different image reading equipment depending on the situation: image reading equipment having a white backing member to obtain images for a recognition processing such as OCR, or image reading equipment having a black backing member for an image processing.
In the conventional method, it is difficult to configure image reading equipment having different backing member into one equipment. Accordingly, it is difficult to use the same equipment both for recognition processing and for image filing processing. In short, two different sets of image reading equipment are required to perform both processing described above.
In addition, recently various software systems have been developed. A single personal computer which has been introduced to conduct a processing by a software can be used for another processing simply by installing another software. A problem arises if image reading equipment which has been purchased for a processing can not be used for another processing, requiring another image reading equipment to be newly purchased.